Topic 9.2: Electrochemical cells

Question 1

Function of voltaic cells

Answer 1

Convert energy from spontaneous, exothermic chemical processes to electrical energy

Question 2

Activity series definition

Answer 2

The metal higher in the activity series is oxidized and the metal lower in the activity series is reduced

Question 3

Electrode potential definition

Answer 3

Tendency of an electrode when it is in contact with the solution of its ions to lose or gain e-

Question 4

What will allow the flow of electrons in a circuit?

Answer 4

A potential difference (voltage) between the electrodes will allow the flow of electrons

Question 5

What reaction occurs at the anode in a voltaic cell? What is its charge?

Answer 5

a) Oxidation

b) Negative electrode

Question 6

What reaction occurs at the cathode in a voltaic cell? What is its charge?

Answer 6

a) Reduction

b) Positive electrode

Question 7

Structure of a voltaic cell

Answer 7

Two half cells are joined by a wire and a salt bridge

Question 8

Half-Cell Definition

Answer 8

Metal in contact with an aqueous solution of its own ions

Question 9

Salt-Bridge Definition

Answer 9

Ions flow through the half-cells to balance out the charges and maintain the ∆ potential

Question 10

Process to conduct electricity in a voltaic cell

Answer 10

1) Electricity is produced because e- flow from the oxidized substance, where electrons are being lost, to the reduced substance, where electrons are being gained (as electrons are electricity)
2) The salt bridge completes the circuit and neutralizes any buildup of charge by the following ion movement:
a) Anions in the salt bridge move from the cathode to the anode
b) Cations move in the salt bridge move from the anode to the cathode

Question 11

Cell diagram of a voltaic cell

Answer 11

a) A single vertical line is used to separate different states of matter on the same side
b) A double vertical line represents a salt bridge between the half-cells
c) The anode (where oxidation occurs) is placed on the left side of the ||
d) The cathode (where reduction occurs) is placed on the right side of the ||
e) Any electrodes that the wires are actually joined to are put at the end of both sides

Question 12

What happens when cells are set up using gases or metal ions but no solid metal?

Answer 12

There is anything that we can physically connect a wire to and so use platinum (a very inert metal) as the electrode

Question 13

Electrolysis

Answer 13

Breaking down of a substance (in molten state) by the passage of electricity through it

Question 14

Function of electrolytic cells

Answer 14

Convert electrical energy to chemical energy by bringing about non-spontaneous processes

Question 15

Structure of electrolytic cells

Answer 15

Electrodes are placed in an electrolyte and connected to the power source by electrical wires

Question 16

Electrolyte definition

Answer 16

Liquid substance (Molten ionic compound / Solution of an ionic compound)

Question 17

Electrodes composition of an electrolytic cell

Answer 17

Made up of an inert, heat resistant material like graphite or platinum

Question 18

Why is the anode positive in an electrolytic cell?

Answer 18

The positive pole of the external power source makes the anode of the electrolytic cell positive

Question 19

Process of an electrolytic cell

Answer 19

a) The electrical energy supplied by the power source induces a flow of electrons from the anode to the cathode
b) When the current reaches the electrolyte, the electrical energy is carried by ions, which move to the electrodes. The redox reactions taking place at the electrodes take the ions of out solution and allow it to continue.

Question 20

How does the flow of energy go in an electrolytic cell?

Answer 20

a) Movement of electrons from anode to anode to the cathode

b) Flow of ions in the electrolyte.

Question 21

What is produced in the electrodes when a substance is electrolyted?

Answer 21

The elements of the ions which that salt is made up

Question 22

Cell diagram of a voltaic cell with Platinum inert electrodes

Answer 22

Pt(s) | H2(g), H+(aq) || Fe3+(aq), Fe2+(aq) | Pt(s)

Question 23

Differences between electrolytic and voltaic cells in terms of:

a) Voltage
b) Spontaneity of reaction

Answer 23

a) Required | Produced

b) Non-spontaneous | Spontaneous